The Air City Tower (ACT) is a device for the drainage of contaminated urban atmospheres consisting of one or several air propellers, with the air intake at the bottom or on the side and the air output oriented upward, fixed to a support capable of sliding vertically over a structure or an immobile tower of great height (more than 100 m), or to a mobile tower with the propellers' support fixed on the tower that would also move up and down vertically with the propellers' support fixed on the tower, or simultaneously both dispositions; this would allow the propellers to be placed within the stratus of hypercontaminated air that forms at dawn over some urban areas during the anticyclonic periods with thermal inversion and under the level of such inversion, and to suction the supercontaminated air from that stratus projecting it upward several hundreds of meters above the level of inversion until it reached the zones of the atmosphere which enjoy wind speeds sufficient to transport, in a natural way, the pollution diluted in the stream far from the urban area that originated it. Moreover, foreseeing the advantageous existence in the propellers' support of acoustic mufflers, physical-chemical filtrating and decontaminant devices, as well as other systems, at the same time that, when several propellers are in place, those of higher speed would be surrounded by those of lower speed creating a turbo-fan effect that would augment the reach and reduce the sound and the consumption.
The present patent of invention refers to a device for the drainage of contaminated urban atmospheres, during the anticyclonic period and/or with thermal inversion, in which the maximum contamination indices are reached, with the goal of sensibly reducing such indices.
This constitutes a substantial advance in the techniques utilitzed until today to reduce or control the atmospheric pollution, which are directed, almost exclusively, to the control of contaminated sources, such as combustion engine exhausts through catalysts or such as industrial smoke through physical-chemical treatments, which reduce the amount of contaminants emitted daily in a specific urban area.
All these atmospheric contamination control techniques presuppose a system of natural ventilation of breezes or winds over the urban area sufficient to ensure that the quantity of contaminants definitively evacuated each day from the area is larger, or at least similar, to the quantity produced that day.
However, this is not so in periods of several days with totally or almost totally stable atmospheres or, more specifically, in the periods in which, because of the phenomena known as thermal inversion, this substitution of the clean or much less contaminated air by the contaminated air does not occur, where the contamination balance does not increase or accumulate over several days.
In such periods the quantity of contaminants emitted in one day by the urban area accumulates with that of the preceding days, arriving at very high indices of contaminants, despite maintaining control measures over the emitting sources, or other control measures especially reinforced such as the prohibition of automobile circulation, the reduction of heat produced by radiators or the control of the more contaminating industrial processes.
The problem may become as grave as to almost paralyze the activity of an urban area with the enormous economic costs that all of that entails and, worse yet, with the damage inflicted on people's health while waiting for a meteorological change that brings a system of winds and ventilates the area.
It is precisely at this moment in the process, that is to say, in the ventilation of an area where its atmosphere is stagnated due to thermal inversion, when the device here described takes effect. During this phenomena of the inversion of the atmosphere's temperature, which progressively decreases with the altitude, a change or an inversion of such decrease occurs at a determinate level, variable according to the meteorological and geographical conditions, producing, from this level on a constant increase until the thermal decrease caused by altitude is reestablished at a different height.
The graph which shows temperatures according to their altitude above the ground presents a "Z" characteristic of such thermal inversion phenomena, precisely over the layers where the highest concentration of contaminants is retained, because of the effect of such layers of rising temperature as authentic lids for the whole mass of air existing between them and the surface of the city.
An analysis of contamination in the cities according to the altitude of the atmosphere during the anticyclonic and thermal inversion periods has shown that at the hours between midnight and dawn a stratus of very high concentration of contaminants at a given height forms; this stratus is dispersed towards the ground during the first hours of the day due to the effect of the convection currents provoked by the sun's action. The hypercontaminated stratus is several tens of meters thick and is normally located between one hundred and five hundred meters above the ground, depending on the meteorological conditions.